Conflict and Tension: The Inter-War Years, 1918–1939

What you'll learn

This revision guide covers the period between the two World Wars, examining why the peace settlement of 1919 failed to prevent another devastating conflict. You'll explore the aims of the peacemakers at Versailles, the structure and effectiveness of the League of Nations, and the chain of diplomatic crises that led to the outbreak of World War Two in September 1939.

Key terms and definitions

Treaty of Versailles — the peace settlement signed in June 1919 between the Allied powers and Germany, imposing harsh territorial, military and financial terms on the defeated nation

League of Nations — an international organisation established in 1920 to maintain world peace through collective security and diplomatic negotiation

Collective security — the principle that member states of the League would act together to stop aggression by any nation, using economic sanctions or military force

Appeasement — the British and French policy of making concessions to aggressive powers (especially Nazi Germany) in the 1930s to avoid war

Mandate — a former German colony or Ottoman territory administered by a League of Nations member on behalf of the League

Reparations — compensation payments demanded from Germany by the Allies for war damage, set at £6,600 million in 1921

Anschluss — the political union between Austria and Germany, forbidden by Versailles but achieved by Hitler in March 1938

Sudetenland — the German-speaking border region of Czechoslovakia claimed and occupied by Hitler in 1938

Core concepts

The peace settlement: aims and outcomes (1918-1920)

The Paris Peace Conference opened in January 1919 with conflicting aims among the "Big Three" leaders. Georges Clemenceau of France demanded harsh treatment of Germany to ensure French security, seeking:

• German territory along the Rhine to act as a buffer zone
• Massive reparations to rebuild French infrastructure
• Permanent German military weakness

Woodrow Wilson of the USA promoted his idealistic Fourteen Points, advocating:

• Self-determination for national groups
• A League of Nations to prevent future wars
• Fair treatment of Germany to avoid future resentment
• Freedom of the seas and free trade

David Lloyd George of Britain occupied a middle position, wanting:

• Germany punished but not destroyed (to maintain trade)
• German colonies distributed among the victors
• Prevention of the spread of communism from Russia

The final Treaty of Versailles represented an uneasy compromise. Germany lost 13% of its territory, including Alsace-Lorraine to France, the Polish Corridor to Poland, and all overseas colonies. The Rhineland was demilitarised and occupied by Allied troops. Germany's armed forces were reduced to 100,000 men, with no air force, submarines or tanks permitted. Article 231, the War Guilt Clause, forced Germany to accept full responsibility for starting the war.

Other treaties completed the peace settlement: St Germain with Austria, Trianon with Hungary, Neuilly with Bulgaria, and Sèvres with Turkey. These treaties redrew the map of Europe, creating new states like Czechoslovakia and Yugoslavia through the application of self-determination, though this principle was inconsistently applied.

Reactions to the Treaty of Versailles

German reactions were overwhelmingly hostile. The new Weimar government had no choice but to sign what Germans called the Diktat (dictated peace) in June 1919. Germans resented:

• The War Guilt Clause as a humiliating lie
• Reparations as economically crippling
• Territorial losses, particularly the Polish Corridor separating East Prussia from the rest of Germany
• The contrast between Wilson's Fourteen Points and the harsh reality
• Being excluded from the League of Nations

This resentment created the "stab in the back" myth, with extremists claiming the army had been betrayed by politicians who signed the treaty. This narrative would later help Hitler's rise to power.

Allied reactions were mixed. France felt the treaty was too lenient, as Germany remained potentially powerful and unified. Britain soon regretted the harshness, fearing it would drive Germany toward communism or extremism. The USA refused to ratify the treaty, with the Senate rejecting both the treaty and League membership, retreating into isolationism.

Structure and organisation of the League of Nations

The League's structure included four main bodies:

The Assembly met annually with representatives from all member states. Each nation had one vote, and decisions required unanimous agreement, making rapid action difficult.

The Council met more frequently and included permanent members (originally Britain, France, Italy and Japan) plus temporary members elected by the Assembly. The Council could recommend action against aggressor nations.

The Secretariat functioned as the League's civil service, preparing reports and keeping records.

The Permanent Court of International Justice at The Hague settled legal disputes between nations.

The League could apply three types of pressure against aggressive nations:

• Moral condemnation — publicly criticising aggressive actions
• Economic sanctions — members refusing to trade with the aggressor
• Military sanctions — members contributing forces to stop aggression

The League's agencies achieved notable humanitarian successes, including:

• Repatriating 400,000 prisoners of war
• Settling refugee crises in Turkey and Greece
• Combating slavery and disease through the Health Organisation
• Improving working conditions via the International Labour Organisation

Successes and failures of the League in the 1920s

The League successfully resolved several disputes in the 1920s:

Åland Islands (1921) — The League ruled these islands between Sweden and Finland should remain with Finland, and both countries accepted the decision.

Upper Silesia (1921) — After a plebiscite in this disputed industrial region between Germany and Poland, the League divided the territory, satisfying both nations.

Greece-Bulgaria (1925) — When Greek troops invaded Bulgaria after a border incident, the League ordered withdrawal and Greece complied, paying compensation.

However, significant failures revealed the League's limitations:

Vilna (1920) — Poland seized this Lithuanian capital and the League failed to act, as neither Britain nor France would send troops against Poland.

Corfu (1923) — When Mussolini bombarded and occupied this Greek island after an Italian official's murder, the League sided with Italy under pressure from Mussolini. This showed that powerful nations could ignore the League.

The Ruhr Crisis (1923) — France and Belgium invaded Germany's industrial heartland when reparations payments fell behind. The League proved powerless as France was a permanent Council member.

These failures demonstrated that the League could only act against small nations when great powers agreed to support action.

The collapse of international order in the 1930s

The 1929 Wall Street Crash and subsequent Great Depression undermined international cooperation. Nations focused on domestic economic problems, turning to protectionism and nationalism. Extremist leaders came to power promising to restore national greatness through aggressive foreign policies.

The Manchurian Crisis (1931-1933) exposed the League's inability to restrain great powers. Japan, a permanent Council member, invaded Manchuria (part of China) following the Mukden Incident. China appealed to the League, which sent the Lytton Commission to investigate. The Commission took a year to report, eventually condemning Japan's actions. Japan simply left the League in 1933 and kept Manchuria. Britain and France refused to apply sanctions, fearing damage to their trade during the Depression and lacking military forces in the Far East.

The Abyssinian Crisis (1935-1936) proved even more damaging. Mussolini's Italy invaded Abyssinia (modern Ethiopia), one of only two independent African states and a League member. Emperor Haile Selassie appealed to the League, which imposed economic sanctions but excluded vital oil supplies. Britain and France secretly negotiated the Hoare-Laval Pact to give Mussolini most of Abyssinia, though public outrage forced them to abandon this plan. Italy conquered Abyssinia by May 1936 and left the League. This crisis destroyed the League's credibility and pushed Mussolini toward alliance with Hitler.

Hitler's foreign policy and the road to war (1933-1939)

Hitler's aims for German foreign policy were clearly stated in Mein Kampf:

• Destroy the Treaty of Versailles
• Unite all German-speaking peoples in a greater Germany
• Acquire Lebensraum (living space) in Eastern Europe
• Destroy communism

Hitler withdrew Germany from the League and Disarmament Conference in 1933. In 1934, he attempted Anschluss with Austria but backed down when Mussolini moved troops to the border. In 1935, Hitler reintroduced conscription, openly rearming Germany in violation of Versailles. Britain responded with the Anglo-German Naval Agreement, allowing Germany to build up to 35% of British naval tonnage.

In March 1936, Hitler remilitarised the Rhineland, sending troops into the demilitarised zone. This gamble succeeded as Britain and France failed to respond militarily. Many British people felt Germany was "walking into its own backyard" and opposed military action. France would not act without British support.

Hitler achieved Anschluss in March 1938 after Austrian Nazis created chaos and the Austrian Chancellor requested German intervention. German troops entered Austria unopposed, and Hitler declared union between the two countries. Britain and France protested but took no action.

The Sudeten Crisis and Munich Agreement (1938)

Hitler next demanded the Sudetenland, where three million German-speakers lived under Czech rule. He encouraged the Sudeten Nazi Party to create unrest, then threatened war to "protect" these Germans. British Prime Minister Neville Chamberlain flew to Germany three times to negotiate, practising appeasement to prevent war.

At Munich in September 1938, Britain, France, Germany and Italy agreed that Germany could occupy the Sudetenland. Czechoslovakia was not invited to the conference. Chamberlain returned to Britain claiming "peace for our time." The Munich Agreement is often seen as the height of appeasement's failure, as Hitler was emboldened to make further demands.

In March 1939, Hitler broke his Munich promises by occupying the rest of Czechoslovakia, ending any pretence of merely uniting German-speakers. Britain and France finally abandoned appeasement, guaranteeing Poland's independence.

The outbreak of World War Two (1939)

Hitler next demanded Danzig and the Polish Corridor. Throughout summer 1939, tension mounted as Britain and France prepared for war while seeking a Soviet alliance. Stalin, suspicious of Western intentions after Munich excluded the USSR, negotiated with both sides.

In August 1939, the world was shocked by the Nazi-Soviet Pact (Molotov-Ribbentrop Pact). These ideological enemies agreed not to fight each other and secretly divided Poland between them. The Pact gave Hitler freedom to attack Poland without fearing Soviet intervention or a two-front war.

On 1 September 1939, German forces invaded Poland using Blitzkrieg (lightning war) tactics. Britain and France issued an ultimatum demanding withdrawal. When Hitler ignored this, both countries declared war on 3 September 1939. The League's failure to prevent aggression and the policy of appeasement had ultimately failed to maintain peace.

Worked examples

Question 1 (4 marks): Describe two problems faced by the League of Nations in trying to keep peace.

Model answer:

One problem was that not all major powers were members. The USA never joined as the Senate rejected the Treaty of Versailles, meaning the League lacked the world's most powerful economy and military to support its decisions. Without American involvement, sanctions were less effective.

Another problem was that the League lacked its own armed forces. Member states had to volunteer troops to stop aggression, but nations like Britain and France were unwilling to risk their soldiers in distant conflicts, particularly after World War One's casualties. This meant military action was almost impossible.

Examiner comment: This answer gains full marks (2+2) by identifying two distinct problems and developing each with specific supporting detail showing understanding of why each was significant.

Question 2 (12 marks): Explain why the Treaty of Versailles caused problems in international relations in the years up to 1923.

Model answer:

The Treaty caused problems because Germany deeply resented its terms and sought to undermine or revise them. Germans believed the War Guilt Clause was unjust as they felt they had not caused the war alone. This resentment created political instability in Germany, with extremist groups using opposition to Versailles to gain support. The treaty's harsh terms gave Germans a common enemy and undermined support for the democratic Weimar government that signed it.

The reparations demands created immediate economic problems and international tensions. Set at £6,600 million in 1921, these payments strained Germany's recovering economy. When Germany fell behind on payments, France and Belgium invaded the Ruhr in 1923, Germany's industrial heartland, to seize goods in lieu of payment. This illegal action showed how Versailles disputes could escalate to military action and revealed the League's powerlessness when permanent members broke international law.

The territorial changes also caused ongoing disputes. The Polish Corridor separated East Prussia from the rest of Germany, creating resentment and a territorial grievance Hitler would later exploit. The port of Danzig became a Free City under League control, satisfying neither Germany nor Poland. In the Vilna dispute of 1920, Poland seized Lithuania's capital, and neither the League nor the Western Allies forced Poland to withdraw, showing inconsistent application of self-determination and encouraging further treaty violations.

Finally, excluding Germany from the League until 1926 created a two-tier international system where the defeated powers were treated as outcasts. This contradicted Wilson's desire for a fair peace and created German determination to overturn the settlement when strong enough.

Examiner comment: This answer would achieve Level 4 (10-12 marks) as it provides a multi-causal explanation with clear links between the treaty's terms and specific international problems, using accurate supporting knowledge and reaching a clear overall judgement about causation.

Question 3 (16 marks + 4 SPaG): "The main reason the League of Nations failed in the 1930s was the Manchurian Crisis." How far do you agree with this statement?

Model answer structure:

Introduction: Brief context about the League's decline in the 1930s and statement of argument (e.g., "While Manchuria damaged the League's authority, multiple factors combined to cause its failure.")

Paragraph supporting the statement: Explain how Manchuria showed the League couldn't control a great power aggressor. Japan's success in ignoring the Lytton Report and keeping its conquest demonstrated that permanent members could act with impunity. This encouraged Mussolini and Hitler to believe they too could ignore the League.

Paragraphs offering alternative factors:

• The Abyssinian Crisis was equally or more important as it directly involved European powers and the betrayal via the Hoare-Laval Pact destroyed any remaining credibility. Haile Selassie's speech to the Assembly symbolised the League's moral collapse.
• The absence of the USA from the start meant the League lacked the economic and military muscle to enforce decisions. Without America, sanctions were ineffective as aggressive nations could trade with non-members.
• The Depression made countries prioritise domestic recovery over collective security, undermining willingness to enforce sanctions that might harm their own economies.

Conclusion: Reach a balanced judgement weighing the significance of Manchuria against other factors, explaining which was most important and why (with clear criteria for judgement).

Examiner comment: Top-level answers (13-16 marks) analyse multiple factors, make links between them, and reach a sustained judgement supported by accurate, detailed knowledge. SPaG marks require consistent accuracy in spelling, punctuation, grammar, and use of historical terminology.

Common mistakes and how to avoid them

• Confusing the different Paris peace treaties — Remember Versailles was with Germany only. Learn the other Central Powers' treaties (St Germain, Trianon, Neuilly, Sèvres) and their main terms.

• Treating appeasement as purely cowardice — Understand the context: war-weariness after 1914-18, economic problems from the Depression, military unpreparedness, and some sympathy for German grievances about Versailles. Explain why leaders like Chamberlain genuinely believed appeasement could preserve peace.

• Assuming the League had an army — The League relied entirely on member states volunteering forces, which they were reluctant to do. This structural weakness was crucial to understanding its failures.

• Oversimplifying Hitler's aims — Avoid stating Hitler "just wanted war." Explain his specific objectives (destroying Versailles, uniting German-speakers, gaining Lebensraum, defeating communism) and how his tactics evolved.

• Ignoring chronology in 16-mark essays — When explaining why something happened, trace the development over time rather than jumping between periods. Show how earlier events influenced later ones.

• Writing narratives instead of explanations — In "explain why" questions, focus on causes and consequences, not just describing what happened. Every paragraph should answer the "why" question directly.

Exam technique for "Conflict and Tension: The Inter-War Years, 1918–1939"

• Master command words: "Describe" requires factual recall (4 marks); "Explain why" needs causes with supporting detail (12 marks); "How far do you agree" demands evaluation of multiple factors with a sustained judgement (16 marks plus 4 SPaG).

• Use the mark scheme structure: For 12-mark questions, aim for three developed paragraphs each explaining a different reason. For 16-mark essays, write 4-5 paragraphs including introduction, arguments for and against the statement, and a conclusion with clear judgement.

• Deploy precise factual support: Don't just state "the Treaty was harsh" — specify "Germany lost 13% of territory including the Polish Corridor and all colonies, while the army was reduced to 100,000 men." Specific details demonstrate knowledge and make analysis more convincing.

• Link factors explicitly: Especially in 16-mark answers, show how factors connect. For example: "The Manchurian Crisis emboldened Mussolini because it proved the League wouldn't act against great powers, which encouraged his invasion of Abyssinia three years later."

Quick revision summary

The inter-war years saw attempts to build lasting peace through the Treaty of Versailles and League of Nations fail dramatically. German resentment of Versailles, the League's structural weaknesses (especially US absence and lack of armed forces), and the Depression's economic impact undermined collective security. The League failed to stop Japanese aggression in Manchuria or Italian conquest of Abyssinia. Hitler systematically destroyed Versailles through rearmament, remilitarisation of the Rhineland, Anschluss and seizing Czechoslovakia while Britain and France pursued appeasement. The Nazi-Soviet Pact enabled Hitler's invasion of Poland, beginning World War Two in September 1939.